Cross talk compensation circuit

ABSTRACT

A low cross talk compensation circuit comprising a first signal pair having a first conductor and a second conductor parallel to the first conductor, and a second signal pair having a third conductor and a fourth conductor parallel to the third conductor, wherein each conductor is attached to a corresponding input signal. A first compensation line attached to the first input signal and a second compensation line attached to the third input signal are intertwined forming a first compensation line assembly with capacitive and inductive coupling parallel to and flanked by the second and third conductors. A third compensation line attached to the fourth input signal and a fourth compensation line attached to the second input signal are intertwined forming a second compensation line assembly with capacitive and inductive coupling parallel to and adjacent to the second conductor.

FIELD OF THE INVENTION

[0001] The present invention relates to a transmission medium, and moreparticularly, to a low cross talk electrical signal transmission medium.

BACKGROUND OF THE INVENTION

[0002] The United States Federal Communications Commission (FCC) hasadopted standards for electrical connectors used in thetelecommunications industry to ensure intermateability. The mostcommonly utilized electrical connector is a modular plug and jack. Theplug is typically terminated to a cable having a plurality of parallelconductors that are paired to form a signal loop, and the jack iscommonly mounted to a panel or a printed circuit board connected to acommunications network. As the modular plugs are utilized morefrequently in high frequency data and communication applications,interference or cross talk that arises in adjacent and parallel contactsof the jack, and to a lesser degree in the plug, has become a problem inthe industry. When an electrical signal of a given frequency is appliedto a pair of conductors, an unequal portion of signal energy istransmitted to the individual conductors of an adjacent pair by eachconductor of the signal pair. This transmission is primarily due tocapacitive and inductive couplings between adjacent conductors beingsubstantially higher than couplings of the other conductor of the signalpair, resulting in cross talk. Cross talk is further increased when bothconductors of the signal pair are placed adjacent to and outside ofopposing conductors of the other signal pair. The magnitude of the crosstalk is effected by such factors as the positioning of the conductors,the distance between adjacent conductors and the dielectric materialbetween the conductors.

[0003] It has been found that cross talk coupling induced by the plugand jack interface can be reduced by shifting the placement of theconductors after they exit the jack so as to induce signals of oppositephase to those which were induced inside the plug and jack. To decreasecross talk, the conductors that form both pairs should be routed in apattern that is opposite in polarity to the pattern that produces crosstalk in the jack and plug. One such routing method is disclosed in U.S.Pat. No. 5,299,956 and U.S. Pat. No. 5,310,363 issued to Brownell et al.Brownell et al. teaches a low cross talk transmission assemblycomprising an electrical connector having a first and second conductorforming a first signal pair and a third and fourth conductor forming asecond signal pair. The first and second conductors are positionedadjacent and parallel to each other. The third conductor is positionedadjacent and parallel to the first conductor, and the fourth conductoris positioned adjacent and parallel to the second conductor. Becausethis arrangement induces cross talk from one signal pair to anothersignal pair when signals are applied to either one of the pairs, thethird conductor is routed adjacent to and parallel to the secondconductor and away from the first conductor, and the fourth conductor isrouted adjacent and parallel to the first conductor and away from thesecond conductor. This new path configuration reduces a substantialamount of cross talk induced in the first configuration.

[0004] An alternative solution to the cross talk problem is disclosed inU.S. Pat. No. 5,488,201 issued to Liu. In Liu a first end of a firstconductor and a first end of a third conductor are folded into bendsthat are mutually inserted into each other and alternately arranged.Also, a first end of a second conductor and a first end of a fourthconductor are folded into bends that are mutually inserted into eachother and alternately arranged. The alternating arrangement of the firstand third conductors and the second and fourth conductors reduces theamount of cross talk between the conductors by forming a mutuallycorresponding capacitive arrangement for restoring electrical balance ofthe conductive pairs. This design, however, is intricate and requirescomplex configurations of the conductors to decrease the amount of crosstalk. Further, the configurations are predisposed and therefore can notbe manipulated to change impedance without manufacturing additionalproducts having additional configurations.

[0005] It is therefore desirable to develop a less intricate design thatmay be easily manipulated to change impedance for partial cancellationof cross talk induced into a signal carrying cable pair by modular jacksand plugs, or other input/output signal connectors, while maintainingproper longitudinal balance and characteristics within the connectorsystem.

SUMMARY OF THE INVENTION

[0006] This invention relates to a low cross talk electrical signaltransmission assembly comprising a signal transmission medium having afirst signal pair and a second signal pair. The first signal pair havinga first conductor and a second conductor. The second signal pair havinga third conductor and a fourth conductor. Each conductor is attached toa corresponding input signal. A first compensation line is attached tothe first input signal, and a second compensation line is attached tothe third input signal. The first compensation line and the secondcompensation line are intertwined to create a first compensation lineassembly having capacitive and inductive coupling. A third compensationline is attached to the fourth input signal, and a fourth compensationline is attached to the second input signal. The fourth compensationline and the third compensation line are intertwined to create a secondcompensation line assembly with capacitive and inductive coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention will now be described by way of example withreference to the accompanying figures in which:

[0008]FIG. 1 is a top view of a first side of a circuit board showing anembodiment of the low cross talk compensation circuit of the presentinvention.

[0009]FIG. 2 is a top view of a second side of the circuit board showingthe low cross talk compensation circuit of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]FIGS. 1 and 2 show a first side 20 and a second side 30 of aprinted circuit board 10, respectively. The printed circuit board 10contains a plurality of signal input contacts 1, 2, 3, 4, 5, 6, 7, 8 anda plurality of signal output contacts 21, 22, 23, 24, 25, 26, 27, 28.The signal input contacts 1, 2, 3, 4, 5, 6, 7, 8 are electricallyconnected to the signal output contacts 21, 22, 23, 24, 25, 26, 27, 28by four signal pairs 11, 12, 13, 14. Each signal pair 11, 12, 13, 14 hasa tip (T) conductor and a ring (R) conductor. A first signal pair 11comprises a ring conductor R1 and a tip conductor T1. A second signalpair 12 comprises a ring conductor R2 and a tip conductor T2. A thirdsignal pair 13 comprises a ring conductor R3 and a tip conductor T3, anda fourth signal pair 14 comprises a ring conductor R4 and a tipconductor T4. The conductors T1, R1, T2, R2, T3, R3, T4, and R4 arerepresented by circuit trace lines on the printed circuit board 10.

[0011] The electrical connection of the printed circuit board 10 willnow be described in greater detail. As shown in FIG. 1, on the firstside 20 of the printed circuit board 10, the signal input contact 2 iselectrically connected to the signal output contact 22 by the conductorR3. The signal input contact 5 is electrically connected to the signaloutput contact 25 by the conductor T1. The signal input contact 6 iselectrically connected to the signal output contact 26 by the conductorR2. The signal input contact 8 is electrically connected to the signaloutput contact 28 by the conductor R4. The conductor R4 and theconductor R3 are routed from their corresponding signal input contacts8, 2 to their corresponding signal output contacts 28, 22 adjacent andparallel to each other. The conductor T1 is routed from the signal inputcontacts 5 to the signal output contact 25 adjacent and parallel to theconductor R4. The conductor R2 is routed from the signal input contacts6 to the signal output contact 26 adjacent and parallel to the conductorR3. The conductors T1 and R2 thereby flank the conductors R4 and R3.

[0012] As shown in FIG. 1, the signal input contact 4 and the signalinput contact 6 are electrically connected to conductors 34, 36,respectively. The conductor 34 has a first end 61 connected to thesignal input contact 4 and a second end 62 connected to a first part 51of an insulated compensation line 44. The first part 51 of the insulatedcompensation line 44 is stripped prior to connection to the second end62. The conductor 36 has a first end 63 connected to the signal inputcontact 6 and a second end 64 connected to a first part 53 of aninsulated compensation line 46. The first part 53 of the insulatedcompensation line 46 is stripped prior to connection to the second end64. The insulated compensation lines 44, 46 are twisted to intertwinethe compensation line 44 and the compensation line 46 to form acompensation line assembly 40. The compensation line assembly 40 ispositioned substantially parallel to the printed circuit board 10 andsubstantially parallel to and adjacent to the conductor R4 and theconductor R3. Second parts 52, 54 of the compensation lines 44, 46,respectively, remain unattached to the printed circuit board 10. Thesecond parts 52, 54 may alternatively be tacked or otherwise attached tothe circuit board 10 for example by soldering them to a non-electricalpad or via on the circuit board 10. It should be appreciated by thoseskilled in the art that the first parts 51, 53 of the compensation lines44, 46 may be attached directly to the signal input contacts 4, 6, toobtain a substantially similar result. It should also be understood thatthe length of the compensation line assembly 40 may be varied to achievevarious levels of crosstalk compensation.

[0013] The signal input contact 3 and the signal input contact 5 areelectrically connected to conductors 33, 35, respectively. The conductor33 has a first end 65 connected to the signal input contact 3 and asecond end 66 connected to a first part 55 of an insulated compensationline 43. The first part 55 of the insulated compensation line 43 isstripped prior to connection to the second end 66. The conductor 35 hasa first end 67 connected to the signal input contact 5 and a second end68 connected to a first part 57 of an insulated compensation line 45.The first part 57 of the insulated compensation line 45 is strippedprior to connection to the second end 68. The insulated compensationlines 43, 43 are twisted to intertwine the compensation line 43 and thecompensation line 45 to form a compensation line assembly 50. Thecompensation line assembly 50 is positioned substantially parallel tothe printed circuit board 10 and substantially parallel to and adjacentto the conductor T1. Second parts 56, 58 of the compensation lines 43,45, respectively, remain unattached to the printed circuit board 10. Thesecond parts 52, 54 may alternatively be tacked or otherwise attached tothe circuit board 10 for example by soldering them to a non-electricalpad or via on the circuit board 10. It should be understood by thoseskilled in the art that the first parts 55, 57 of the compensation lines43, 45 may be attached directly to the signal input contacts 3, 5, toobtain a substantially similar result. It should also be understood thatthe length of the compensation line assemble 40 may be varied to achievevarious levels of crosstalk compensation.

[0014] As shown in FIG. 2, on the second side 30 of the printed circuitboard 10, the signal input contact 1 is electrically connected to thesignal output contact 21 by the conductor T3. The signal input contact 3is electrically connected to the signal output contact 23 by means ofthe conductor T2. The signal input contact 4 is electrically connectedto the signal output contact 24 by means of the conductor R1. The signalinput contact 7 is electrically connected to the signal output contact27 by means of the conductor T4. The conductor T3 and the conductor T4are routed from their corresponding signal input contacts 1, 7 to theircorresponding signal output contacts 21, 27 adjacent and parallel toeach other. The conductor T2 is routed from the signal input contacts 3to the signal output contact 23 adjacent and parallel to the conductorT3. The conductor R1 is routed from the signal input contact 4 to thesignal output contact 24 adjacent and parallel to the conductor T4. Theconductors T2 and R1 thereby flank the conductors T3 and T4. Theconductors T2, T3, T4 and R1, located on the second side 30 of theprinted circuit board 10, are further positioned substantially parallelto the conductors R2, R4, R3 and T1, respectively, located on the firstside 20 of the printed circuit board 10.

[0015] As shown in FIG. 2, the signal input contact 4 and the signalinput contact 6 are electrically connected to conductors 31, 32,respectively. The conductor 31 has a first end 71 connected to thesignal input contact 4 and a second end 72 connected to a first part 61of an insulated compensation line 41. The first part 61 of the insulatedcompensation line 41 is stripped prior to connection to the second end72. The conductor 32 has a first end 73 connected to the signal inputcontact 6 and a second end 74 connected to a first part 63 of aninsulated compensation line 42. The first part 63 of the insulatedcompensation line 42 is stripped prior to connection to the second end74. The insulated compensation lines 41, 42 are twisted to intertwinethe compensation line 41 and the compensation line 42 to form acompensation line assembly 60. The compensation line assembly 60 ispositioned substantially parallel to the printed circuit board 10 andsubstantially parallel to and adjacent to the conductor T3 and theconductor T4. Second parts 62, 64 of the compensation lines 41, 42,respectively, remain unattached to the printed circuit board 10. Thesecond parts 52, 54 may alternatively be tacked or otherwise attached tothe circuit board 10 for example by soldering them to a non-electricalpad or via on the circuit board 10. The compensation line assembly 60located on the second side 30 of the printed circuit board 10 is furtherpositioned substantially parallel to the corresponding compensation lineassembly 40 located on the first side 20 of the printed circuit board10. It should be appreciated by those skilled in the art that the firstparts 61, 63 of the compensation lines 41, 42 may be attached directlyto the signal input contacts 4, 6, to achieve a substantially similarresult. It should also be understood that the length of the compensationline assembly 40 may be varied to achieve various levels of crosstalkcompensation.

[0016] The signal input contact 3 and the signal input contact 5 areelectrically connected to conductors 37, 38, respectively. The conductor37 has a first end 75 connected to the signal input contact 3 and asecond end 76 connected to a first part 65 of an insulated compensationline 47. The first part 65 of the insulated compensation line 47 isstripped prior to connection to the second end 76. The conductor 38 hasa first end 77 connected to the signal input contact 5 and a second end78 connected to a first part 67 of an insulated compensation line 48.The first part 67 of the insulated compensation line 48 is strippedprior to connection to the second end 78. The insulated compensationlines 47, 48 are twisted to intertwine the compensation line 47 and thecompensation line 48 to form a compensation line assembly 70. Thecompensation line assembly 70 is positioned substantially parallel tothe printed circuit board 10 and substantially parallel to and adjacentto the conductor R1. Second parts 66, 68 of the compensation lines 47,48, respectively, remain unattached to the printed circuit board 10. Thecompensation line assembly 70 located on the second side 30 of theprinted circuit board 10 is further positioned substantially parallel tothe corresponding compensation line assemblies 50 located on the firstside 20 of the printed circuit board 10. It should be understood bythose skilled in the art that the first parts 65, 67 of the compensationlines 47, 48 may be attached directly to the signal input contacts 3, 5,to achieve a substantially similar result. It should also be understoodthat the length of the compensation line assembly 40 may be varied toachieve various levels of crosstalk compensation.

[0017] Advantageously, the impedance of the compensation assemblies 40,50, 60, 70 may be varied by increasing or decreasing the number oftwists in the pairs of compensation lines 44 and 46, 43 and 45, 41 and42, 47 and 48. While the present invention has been described inconnection with the illustrated embodiments, it will be appreciated andunderstood that modifications may be made without departing from thetrue spirit and scope of the invention. For example, it should beappreciated by one skilled in the art that the number and location ofthe signal pairs, the number and location of the conductors, as well asthe number and location of the compensation assemblies, may be increasedor decreased to obtain substantially similar results.

What is claimed is:
 1. A low cross talk electrical signal transmissionassembly having a signal transmission medium and further comprising: afirst signal pair having a first conductor and a second conductor; asecond signal pair having a third conductor and a fourth conductor; afirst input signal having the first conductor attached thereto; a secondinput signal having the second conductor attached thereto; a third inputsignal having the third conductor attached thereto; a fourth inputsignal having the fourth conductor attached thereto; a firstcompensation line attached to the first input signal; and a secondcompensation line attached to the third input signal and intertwinedwith the first compensation line to create a first compensation lineassembly having capacitive and inductive coupling.
 2. The low cross talkelectrical signal transmission assembly of claim 1, further comprising afifth conductor having a first end connected to the first input signaland a second end attached to the first compensation line.
 3. The lowcross talk electrical signal transmission assembly of claim 1, whereinthe first conductor and the third conductor are ring conductors and thesecond conductor and the fourth conductor are tip conductors.
 4. The lowcross talk electrical signal transmission assembly of claim 1, whereinthe first conductor and the third conductor are tip conductors and thesecond conductor and the fourth conductor are ring conductors.
 5. Thelow cross talk electrical signal transmission assembly of claim 1,wherein the signal transmission medium is a circuit board.
 6. A lowcross talk electrical signal transmission assembly comprising: atransmission medium having a first side and a second side; a firstsignal pair having a first conductor positioned on the second side and asecond conductor positioned parallel to the first conductor on the firstside; a second signal pair having a third conductor positioned on thefirst side and a fourth conductor positioned parallel to the thirdconductor on the second side; a first input signal having the firstconductor attached thereto; a second input signal having the secondconductor attached thereto; a third input signal having the thirdconductor attached thereto; a fourth input signal having the fourthconductor attached thereto; a first compensation line attached to thefirst input signal; and a second compensation line attached to the thirdinput signal and intertwined with the first compensation line to createa first compensation line assembly parallel to and flanked by the secondconductor and fourth conductor with capacitive and inductive coupling.7. The low cross talk electrical signal transmission assembly of claim6, further comprising a third compensation line attached to the fourthinput signal and a fourth compensation line attached to the second inputsignal and intertwined with the third compensation line to create asecond compensation line assembly parallel to and adjacent to the secondconductor with capacitive and inductive coupling.
 8. The low cross talkelectrical signal transmission assembly of claim 6, further comprising afifth conductor having a first end connected to the first input signaland a second end attached to the first compensation line.
 9. The lowcross talk electrical signal transmission assembly of claim 6, whereinthe first conductor and the third conductor are ring conductors and thesecond conductor and the fourth conductor are tip conductors.
 10. Thelow cross talk electrical signal transmission assembly of claim 6,wherein the first conductor and the third conductor are tip conductorsand the second conductor and the third conductor are ring conductors.11. The low cross talk electrical signal transmission assembly of claim6, wherein the signal transmission medium is a circuit board.
 12. A lowcross talk electrical signal transmission assembly comprising: atransmission medium having a first side and a second side; a firstsignal pair having a first conductor positioned on the second side and asecond conductor positioned parallel to the first conductor on the firstside; a second signal pair having a third conductor positioned on thefirst side and a fourth conductor positioned parallel to the thirdconductor on the second side; a first input signal having the firstconductor attached thereto; a second input signal having the secondconductor attached thereto; a third input signal having the thirdconductor attached thereto; a fourth input signal having the fourthconductor attached thereto; a first compensation line attached to thefirst input signal on the first side; and a second compensation lineattached to the third input signal on the first side and intertwinedwith the first compensation line to create a first compensation lineassembly parallel to and flanked by the second conductor and fourthconductor with capacitive and inductive coupling; and a thirdcompensation line attached to the fourth input signal on the first side;and a fourth compensation line attached to the second input signal onthe first side and intertwined with the third compensation line tocreate a second compensation line assembly parallel to and adjacent tothe second conductor with capacitive and inductive coupling.
 13. The lowcross talk electrical signal transmission assembly of claim 12, furthercomprising: a third signal pair having a fifth conductor positioned onthe second side and a sixth conductor positioned on the first side; anda fourth signal pair having a seventh conductor positioned on the firstside and an eighth conductor positioned on the second side, the fifthconductor positioned parallel to the seventh conductor and the eighthconductor positioned parallel to the sixth conductor.
 14. The low crosstalk electrical signal transmission assembly of claim 13, wherein thefifth conductor and the eighth conductor on the second side are flankedby the first conductor and the fourth conductor and the first conductorand sixth conductor of the first side are flanked by the secondconductor and third conductor.
 15. The low cross talk electrical signaltransmission assembly of claim 12, further comprising: a thirdcompensation line attached to the first input signal on the second side;a fourth compensation line attached to the third input signal on thesecond side and intertwined with the third compensation line to create athird compensation line assembly parallel to and flanked by the firstconductor and fourth conductor and parallel to the first compensationline with capacitive and inductive coupling; a fifth compensation lineattached to the fourth input signal on the second side; and a sixthcompensation line attached to the second input signal on the second sideand intertwined with the fifth compensation line to create a fourthcompensation line assembly parallel to and adjacent to the firstconductor and parallel to the second compensation line with capacitiveand inductive coupling.
 16. The low cross talk electrical signaltransmission assembly of claim 12, further comprising a ninth conductorhaving a first end connected to the first input signal and a second endattached to the first compensation line.
 17. A method of reducing crosstalk between two pairs of conductors extending from a first connectorand across a substrate to a second connector, the method comprising:arranging selected ones of the conductors on the substrate adjacent toeach other for coupling their respective electrical signals to eachother and; connecting at least one pair of mutually insulatedintertwined conductors to one end of a pair of selected ones of theconductors extending across the substrate, the mutually intertwinedconductors having a connected end being in electrical contact with theselected ones of the conductors and a free end opposite the connectedend.